1. Field of the Invention
The present invention relates to an optical disk device, and in particular to an optical disk device for writing data onto an optical disk having a track which wobbles in a predetermined period (“wobble”).
2. Description of the Related Art
In an optical disk device for wiring data onto an optical disk such as a CD-R, because of reasons such as unevenness of the optical disk, film characteristics of the optical disk, and wavelength shift in a laser diode (LD), there are cases in which a pit may not be formed at the center of a track and data is written at a position deviated from the track center. During data writing of a CD-R, a light of a replaying power is irradiated in the space period of the data to be written and a signal representing return light from the optical disk is sampled and held to execute a focus servo process and a tracking servo process. When the power is increased from the replaying power to a writing power, the optical constant of the optical system including the LD is changed, causing the laser to deviate from the track center during a pit pattern forming period of the data to be written, thereby degrading the quality of the written or replayed signals.
Because the amount of deviation from the track center varies among optical disk devices, although a constant amount of deviation may be stored in a memory for adjusting the tracking offset during the data writing using the stored amount of deviation, as the amount of deviation is simply a representative value, the tracking cannot always be precisely corrected.
Japanese Patent Laid-Open Publication No. 2000-20968 discloses that, when laser light is irradiated onto an optical disk onto which a wobbled track (or “wobblet”) is formed, an undulation period component contained in a signal representing return light from the optical disk when data is written is detected and the servo balance is adjusted so that the level of this undulation period component is minimized or substantially minimized.
However, there is a problem in that the servo balance cannot be quickly adjusted by simply adjusting the servo balance based on the level of the undulation period component alone. In other words, even when an attempt is made to minimize the size of the undulation period component, because it is unknown whether the laser light should be translated to the right or to the left with respect to the track, there is a problem in that a significant amount of time elapses before the undulation period component can be converged to a minimum value.